1. Field of the Invention
This invention relates to a hydraulic buffer and, more particularly to a hydraulic buffer in which a damping force can be adjusted by a solenoid valve received in a piston rod.
2. Descrition of the Prior Art
In a hydraulic buffer in which a solenoid valve is provided with a tubular spool movable axially of a piston rod, to open and close a bypass path provided in the piston rod, with the solenoid valve built in the piston rod, so that liquid is allowed or not allowed to pass through the bypass path to change a damping force, the liquid passes through the interior of the spool and then radially so that in use the following troubles occur.
By the pressure gradient due to the flow of liquid in a spool and the viscous resistance of liquid, the spool is carried away by the flow having higher speed. Also, when the flow is only in one side of the spool and absent in the other side, for example, liquid enters the spool from one side thereof and leaves the spool from the central portion thereof, the balance of pressure between the front and rear of the spool is upset by pressure reduction due to the flow so that the spool is moved. As a result, the damping force cannot be adjusted, and the timing of adjustment gets out of order due to erroneous operations.